I first want to agree with Hob Bramble. So, I'll try not to restate any compliments he made.
1. Nofollow links - I liked this213 suggestions if they can be implemented without degrading posts and yes this213 has provided me with great help on occasion and has been here a while.
2. I like the subscription for unread posts
3. Categories need to stay simple and broad. Separating out language specifics under programming forum is probably a good idea. The Graphics category could use some mergers. Internet Marketing is fine unless there are topics missing but I like them broken out by specific search engine. I would definitely consider a Networking category. I would also, not definitely, consider working in an office program category that could comprise of tutorials, know-hows, questions, discussions on spreadsheet programs, word processors, presentation programs, PIMs/Email Clients, etc. Though, many could fall under specific OSes but a program could have Windows and Linux installers like OpenOffice or completely platform independent like Google Apps. I know there are whole forums dedicated to nothing but Excel. On a personal level I'd like to see platform specific news or discussions based on the top technology companies mainly Apple, Microsoft, and Google. Additionally, since these companies are the main mobile players then mobile development could easily be worked into their boards. It would help me to be able to check those boards to see if maybe Google has released a new API or the Apple board to see some neat discussions/feature releases on iOS. These company boards would almost have identical sub-categories (though I would keep sub-categorizing at a minimum) but allow the user to select their specific platform. I find these type of posts commonly posted in the General Discussions that come up when I first log in which is nice.
4. Layout, colors - you're just not going to be able to please everyone here. I've always liked Ozzu for it's simplicity, cleanliness, and classy layout of advertisements. It formats correctly to my display and is very professional. In comparison to other forums, which are clearly recognizable as phpBB or some variant, Ozzu is a blessing and is the ideal model organism for what those sites could be. So many forum sites are so junky and tacky. I think people that can't figure out Ozzu are just used to being in that whirlwind. Also, I think for the highest membership the Ads go bye-bye even though they are not intrusive.
5. I think if you can incorporate more technology news then that may at least make Ozzu a daily stop to get a quickie. Maybe if there's a way to feed into the news like when search a stock quote on google. For example, Intuit from google.com/finance gives events, news and related companies. Perhaps there's a way to lightly tap into that.